A large number of fixed and mobile access standards are now available, such as Wideband-Code Division Multiple Access (W-COMA), Universal Mobile Telephone System-Time Division Duplex (UMTS-TDD), CDMA 2000, Wireless-Local Area Network (W-LAN), EDGE etc, all of which belong to the 3rd generation wireless standards. Each type of access standard has its own particular network concept; where Mobile Internet Protocol (Mobile IP) and the General Packet Radio Service (GPRS) tunnelling protocol are the main two concepts. The invention, however, is not limited to the above mentioned concepts.
Using methods presently available, interoperability between different network concepts is not guaranteed. This is mainly due to three obstacles. First, there is a lack of common subscriber profiles, service standards and authentication mechanisms, preventing enforcement of policies relating, but not limited to, access and service authorization, and accounting and mobility in different networks. Second, there is a lack of common Quality of Service (QoS) versus resource allocation paradigm in the access networks, due to a bottom up instead of a top down approach in designing the data link layers with respect to QoS requirements. Third, there is a lack of common higher layer standards in the terminals, preventing service transparency when user terminals, i.e. clients, roam between different networks that carry specific services.
Thus, there is a problem with interoperability between heterogeneous networks mainly because of problems with authentication and service transparency in and between different networks. It is, of course, theoretically possible to harmonise disparate networks at all of the above levels and thus creating interoperability. There is, however, a need for an organic way of integrating heterogeneous networks and thus providing access independent global roaming.